Lithium niobate etchant

Abstract

Oxides of tantalum and niobium are selectively etched using patterned silicon oxide deposited by a low-temperature chemical vapor deposition as a mask and a sulfate flux to selectively remove exposed portions of the tantalum or niobium oxide substrate.

We claim: 
     
       1. A method of making a device comprising a substrate, said substrate comprising at least one composition selected from the group consisting of tantalum and niobium oxides, said method comprising: depositing a mask material on said substrate;   patterning said mask material to expose selected portions of said substrate;   exposing said exposed portions, at a temperature of approximately 400° C. or less, to a liquid fluxing compound comprising at least one Group IA or Group IIA compound or ammonium ions to yield material which can be removed, said fluxing compound comprises at least one member selected from the group consisting of sulfate, acid sulfate, carbonate, and ammonium salts;   and removing said material which can be removed.   
     
     
       2. A method as recited in claim 1 in which said salt comprises Na 2  CO 3 , KHSO 4 , Na 2  SO 4 , NaHSO 4 , K 2  SO 4 , NaHCO 3 , NH 4  HSO 4  or (NH 4 ) 2  SO 4 . 
     
     
       3. A method is recited in claim 1 in which said substrate comprises at least one member selected from the group consisting of LiNbO 3 , LiTaO 3 , K(Ta,Nb)O 3 , Sr 1-x  Ba x  Nb 2  O 6 , and Na.sub.(1-2x) Ba x  Nb 2  O 6 . 
     
     
       4. A method is recited in claim 3 in which said substrate comprises LiNbO 3 . 
     
     
       5. A method as recited in claim 4 in which said mask material comprises at least one member selected from the group consisting of noble metals and silicon oxide. 
     
     
       6. A method as recited in claim 5 in which said depositing is by low temperature chemical vapor deposition. 
     
     
       7. A method as recited in claim 1 comprising the further step of stripping said mask material. 
     
     
       8. A method as recited in claim 7 comprising the further step of fabricating electrodes on selected portions of said substrate. 
     
     
       9. A method as recited in claim 1 in which said removing step comprises dissolving said material in water or an acid. 
     
     
       10. A method as recited in claim 1 in which said fluxing compound is combined with H 2  SO 4 . 
     
     
       11. A method as recited in claim 2 in which said salt is combined with H 2  SO 4 . 
     
     
       12. A method as recited in claim 6 in which said mask material comprises silicon oxide.